1. Technical Field
The present application relates generally to an improved data processing system and method. More specifically, the present application is directed to an intelligent dynamic multiple zone single expander connecting dual ported drives supporting dual initiator and single initiator configurations.
2. Description of Related Art
Storage area networks, or SANs, consist of multiple storage devices connected by one or more fabrics. Storage devices can be of two types: host systems that access data, and storage subsystems that are providers of data. Zoning is a network-layer access control mechanism that dictates which storage subsystems are visible to which host systems. This access control mechanism is useful in scenarios where the storage area network is shared across multiple administrative or functional domains. Such scenarios are common in large installations of storage area networks, such as those found in storage service providers.
One technology that is being used more prevalently with storage area networks is serial attached SCSI (SAS) communication protocol technology. SAS is a computer bus technology primarily designed for transfer of data to and from devices such as hard drives, CD-ROM drives, tape storage devices, and the like. SAS is a serial communication protocol for direct attached storage (DAS) devices. It is designed for the corporate and enterprise market as a replacement for parallel SCSI, allowing for much higher speed data transfers than previously available, and is backwards-compatible with serial advanced technology attachment (SATA) drives. Though SAS uses serial communication instead of the parallel method found in traditional SCSI devices, it still uses SCSI commands for interacting with SAS end devices.
Many servers are already utilizing enterprise class serially attached small computer system interface (serially attached SCSI or SAS) hard disk drives, which are dual ported. In today's non-redundant servers, the two ports of the drive are connected to a single initiator. As the architecture moves to the redundant style, it is necessary for the two ports of the SAS hard disk drives to be connected to two initiators redundantly. Both initiators see both ports on the same SAS hard disk drive (HDD). Early system adopters may need to write/rewrite much of the low level operating system code to handle such dual ported architectures, because current code cannot handle the same resource seen by two initiators.
As disk storage systems continue to increase in density, more drives in a smaller amount of space, it is also becoming increasingly complex to monitor and control all the drives in a system. With the recent adoption of SAS technology HDDs, the number of drives within a given storage domain has been dramatically increased. Theoretical fibre channel (FC) limited is 128 devices while SAS loops may contain 16,384 devices.
Typically, large systems employ a data gathering mechanism known as SCSI enclosure services (SES) to gather the status/control of the disk drives and relay that information back to the system management function. Both FC and SAS HDDs support dual ports to provide for higher availability to the data. SES usually runs separately on both loops; however, the system prefers to see a single uniform mechanism that represents both loops together. Today, this merging of loop information is performed at the lower level hardware pieces, such as on the disk drive enclosure itself with most implementations embedding the SES function within the FC switch or SAS expander. The merger of information may cause problems in the system when the information is being reported differently from each loop. Another disadvantage of this dual loop configuration is the cost of the redundant hardware when most systems may not need the hardware redundancy of the FC switch or SAS expander.